D'Souza Joanita F, Rich Jessima M, Cloherty Shaun L, Price Nicholas S C, Hagan Maureen A
Department of Physiology and Biomedicine Discovery Institute, Monash University, Clayton, Victoria 3800, Australia.
School of Engineering, RMIT University, Melbourne, Victoria 3001, Australia.
eNeuro. 2025 Oct 7;12(10). doi: 10.1523/ENEURO.0287-25.2025. Print 2025 Oct.
Despite various histological, electrophysiological, and imaging studies, the topographic organization of saccade-related activity in the posterior parietal cortex (PPC) has been notoriously difficult to characterize. In part, this is because areas of interest in PPC are often embedded deep in sulci in macaques and humans. Understanding the extent of topographic organization in PPC can provide insights into the computation contributions of PPC. The lissencephalic cortex of the common marmoset offers a unique opportunity to investigate fine-scale topographic organization in PPC. Recordings were obtained from the PPC of two male marmosets performing a visually guided center-out saccade task with 8 or 36 peripheral targets using multichannel electrode arrays with 100 μm spacing. By plotting the pattern of saccade direction tuning preferences across all penetrations and cortical depths, we uncovered topographic organizational features within the PPC. Like other primates, multiunits in marmoset PPC tend to prefer saccade targets in the contralateral visual field. The results detail how preference for saccadic direction changes in a systematic manner across cortical distance, such that response units closer in proximity tend to show systematic changes in their tuning preferences. Across cortical distance, the visual field was also systematically encoded but reversals in direction varied across penetrations. The analysis highlights the likelihood of multiple representations of the visual field for saccade direction preference across PPC. These novel findings suggest a possible functional organization of saccade-related activity in marmoset PPC, giving insights into the computational capacity of the PPC.
尽管进行了各种组织学、电生理学和影像学研究，但后顶叶皮层（PPC）中与扫视相关活动的拓扑组织一直极难表征。部分原因在于，PPC中感兴趣的区域在猕猴和人类中通常深深嵌入脑沟。了解PPC中拓扑组织的范围有助于深入了解PPC的计算贡献。普通狨猴的平滑脑皮层为研究PPC中的精细尺度拓扑组织提供了独特机会。使用间距为100 μm的多通道电极阵列，从两只执行视觉引导的中心向外扫视任务（有8个或36个周边目标）的雄性狨猴的PPC中获取记录。通过绘制所有穿透深度和皮层深度上的扫视方向调谐偏好模式，我们发现了PPC内的拓扑组织特征。与其他灵长类动物一样，狨猴PPC中的多单元倾向于偏好对侧视野中的扫视目标。结果详细说明了扫视方向偏好在皮层距离上如何以系统方式变化，即距离较近的反应单元在调谐偏好上往往表现出系统变化。在整个皮层距离上，视野也被系统编码，但方向反转在不同穿透中有所不同。该分析突出了PPC中扫视方向偏好的视野存在多种表征的可能性。这些新发现揭示了狨猴PPC中与扫视相关活动的一种可能功能组织，有助于深入了解PPC的计算能力。
